A power conversion apparatus is disposed, for example, between a battery and a motor such that the power conversion apparatus controls and supplies an electric power, which is stored in the battery, to the motor. Many child units (e.g., a power module, a reactor, and other units) in a power conversion apparatus, i.e., a PCU (power control unit), mounted in a hybrid vehicle and an electric vehicle generate heat, and performances of the child units may drop due to influences of the generated heat. Thus, the power conversion apparatus needs a cooling structure. A variety of such cooling technologies have been proposed (e.g., Patent Literature Document 1).
The power conversion apparatus disclosed in Patent Literature Document 1 includes a cooler on a casing. The cooler has a liquid inlet for receiving a cooling liquid, and a liquid outlet for discharging the cooling liquid. The cooling liquid flows and circulates through a plurality of connecting passages, which are connected to the liquid inlet and the liquid outlet. A connecting portion between the liquid inlet and the connecting passage(s) is sealed by a sealing part, and a connecting portion between the liquid outlet and the connecting passage(s) is sealed by a sealing part. Each of the sealing parts has a first sealing member for preventing the cooling liquid from leaking to the outside from the connecting portion concerned, a second sealing member for enclosing the first sealing member, and a drain passage provided between the first sealing member and the second sealing member. The drain passage is formed in the casing. The cooling liquid, which stays between the first sealing member and the second sealing member, flows through the drain passage and is discharged out of the casing from the drain exit.
In this structure, however, each of the sealing parts requires the drain passage and the drain exit to discharge the cooling liquid, which stays between the sealing members. As the number of the sealing parts increases, the number of the drain passages and the drain exits increases. This would increase the size of the casing. As a result, there is a concern that the power conversion apparatus may have a larger size.
Patent Literature Document 1: Japanese Patent Application Laid-Open Publication No. 2016-067096